Pneumatic tires are known which have a designated rotational direction and a directional tread pattern corresponding to the rotational direction (see, for example, Japanese Unexamined Patent Application Publication Nos. 2000-229506A and 2005-231430A). In these pneumatic tires, a plurality of main grooves extending in the tire circumferential direction are provided in a tread. A plurality of lands extending in the tire circumferential direction are defined by the main grooves. A plurality of lug grooves extending in the tire width direction are formed in each of the lands. The lug grooves extending from the outer side in the tire width direction toward the inner side are arranged to tilt in the same direction as the rotational direction. Also, in order to ensure rigidity of the lands in which the lug grooves are provided, the end portion of each of the lug grooves on the outer side in the tire width direction opens to one of the main grooves, while the other end portion on the inner side in the tire width direction is closed in one of the lands.
The pneumatic tires having such a directional tread pattern naturally exhibits excellent drainage. The tilt of the lug grooves with respect to the tire width direction enables a pattern noise caused by the lug grooves to be reduced. Furthermore, this configuration has the advantage of exhibiting excellent steering stability, given that the lug grooves are closed at one end, thus ensuring sufficient rigidity of the lands. As such, these pneumatic tires are used as normal tires on local roads, and are also used as-is for circuit driving in competition facilities.
However, in a case where the pneumatic tire having the directional tread pattern that includes the lug grooves closed at one end as described above is used for circuit driving, the rigidity of the portions where the closed end portions of the lug grooves are disposed is relatively low; thus, these portions locally escape from wear due to great deformation during cornering, and conversely, the rigidity of the portions where the closed end portions of the lug grooves are not disposed is relatively high; thus, these portions preferentially undergo wear. As a result, uneven wear over the tire circumference is likely to occur. Then, as uneven wear occurs in the tread, noise after the wear is remarkably worsened. This worsening of noise may not be a problem during circuit driving, but is a cause of loss of comfort during driving on local roads.